AN IMMUNOHISTOCHEMICAL STUDY OF THE ONTOGENY OF THE NEUROENDOCRINE SYSTEM IN THE CHICKEN ESOPHAGUS

The ontogenesis and distribution of serotonin-, chromogranin A-, chrom ogranin B-, galanin-, neurotensin-, bombesin-and neuropeptide Y-immuno reactive elements were studied in the chicken oesophagus during pre-an d post-hatching life. Unlike positive nerve elements, that were presen t in pre-and post-hatching life, positive endocrine cells were observe d only during embryonic life in the oesophageal epithelium. The first endocrine cells, immunoreactive for serotonin and chromogranins, appea red on day 12, in the cervical and thoracic portions of the oesophagus . At the same age, but only in its distal portion, a few bombesin-and neurotensin-immunoreactive cells also appeared. The number of the endo crine cells progressively increased, reaching a maximum on day 15. The y then decreased, with a cranio-caudal progression, until they disappe ared a few days after hatching. Almost all the serotonin-immunoreactiv e cells but only a subpopulation of bombesin-and neurotensin-immunorea ctive cells colocalized chromogranins. About half of this subpopulatio n also colocalized serotonin. All these cells reacted positively with Grimelius argyrophile stain. The mucosa of the crop never contained po sitive endocrine cells. Positive nervous elements appeared first in th e wall of the terminal oesophagus and only one or two days later in th e proximal oesophagus including the crop. Nervous elements immunoreact ive for galanin first appeared from days 6 to 7, for neurotensin from days 7 to 8, for neuropeptide Y from 13 to 15 and for bombesin from 15 to 18. At day 15 galanin-immunoreactive ganglionic cells and fibres o ccupied both the myenteric and submucous plexus and galanin-positive n erve fibres could be seen throughout the oesophageal wall from the adv entitia to a thin subepithelial network. Neurotensin and neuropeptide Y-immunopositive ganglionic cells and fibres, by contrast, invariably occupied the muscular and submucous layers. Scattered bombesin-immunor eactive ganglionic cells were observed only in the myenteric plexus. T he number of positive nerve elements progressively increased until som e weeks after birth. Density and intensity were always much higher for galanin and neurotensin than for neuropeptide Y and bombesin.